Bituminous composition



Patented Jan. 8, 1952 UNITED} STATES PATENT OFFICE b view ng.Application August 23'," 1945,

Serial' N0.-612,284

' i 3 Claims.

This invention relates tosolvent' thinned-him minous composition adaptedto be applied in a fluid or semifluid'state, th'esolventbeingvolatile sothat, after application of thecom'position, the composition becomesstiffened due to' lo'ss of the solvent thereirom by evaporation;Thisfin've'n tion relates particularly to solvent thinned bituminouscomposition adapted for cold process" built-up roofing construction, Incold process built-up roofing construction the bituminous composition isthinned by means of a volatile solvent so that the composition issufiiciently workable at atmospheric temperatures, or whenonly mildlywarmed, to permit manual application of the composition for the purposeof bonding sheets of felt or the like together andprovide layers ofwaterproofing adhesive between such sheets of felt or the like in abuiid-up-type of bituminous roofing.

it is an object of the invention to aiford a solvent thinned bituminouscomposition suitable for application to provide a waterproofingtlayerfor adhesively uniting the plies of a ibuilt-upiroofing, whichbituminous composition as disposed in the fabricated built-dip roofingwill have high fire resistance and will impart high fire resistanceproperties to' the built-up roofing asa whole, While the specialbituminous compositionof this invention is especialiy' designed forusebetween plies oi built-up roofing, the special composition 'oi thisinvention can, if desired; be usedto provide a highly fire resistantsurface coating of built-up roofing or to provide a highlyfire-resistant; water-resistant adhesive for varioussheet ma-"- terials.i

In the construction of built-up roofing, the plies of felt or thelike'aregenerallybonded to ether by so-called mopping-asphalt, namelyroofing grade-asphalt having -a'soitening point or" about 140 F; to 206Frand which can-readily be heatliquefied on the job andtspread with amop or similar implement. Occasionally i the mopping asphalt contains amineralfiller-such as. limestone dust or slate flour in an amou ntsuchas 28% to 30% by weight oftthe composition; but incommon practice isusedwithout anyfiller.

Built-up roofings, ifmade of-a sufiicient-num (Ch IMF-282i madehaverelatively low'resistan'c'e to spread of flame alongthesurfacethereof particularly underthe influence of wind. This poor resistance tospread of flame is due largely to the combustibility of the moppinasphalt. Even when the sheetmaterial is composed of'asbestos felt andeven -when the mopping asphalt is used only in layersbeneaththe toplayer of felt; the roofing a has'poor resistanceto spread of flame dueto the her of plies of sheet material and-particularlytif made up usingasbestos felt sheetmaterial for the several plies of the roofing, or ifsurfaced with properties.

combustible mopping I asphalt and saturant asphaltbleeding out to thesurface, and melting and flowing out" from between the plies, thusforming areas which-burn readily and carry the flame-along the suriaceofthe roofing. More-- oven-since the mopping asphalt becomes heatliquefied and very thin and non-adhesive upon exposure :of the roofingto flame, any wind is apt to raise up the plies of sheet material, andwhen this happens the air is taken into thGbOdyOf the roofing themoppingzasphalt is burned rap idlygivand the'entire roofing burns veryactively and soon ignites the underlyin roof deck.

The"useofsolvent-thinned asphalt to adhesivelybond the plies of abuilt-uproofing so that the asphalt may :beapplied as acold compositioninstead oflina heat liquefied condition, hasbeen very-limited due to thefact that the solvent tends to become entrapped between the plies of theroofingl- It may be added, that whena volatile solventis employedthepresence of the solvent thatis-retained in the finishedrooflngaggravates thecomb'ustibility of theroofing. For this reason; theprovision of a highly fire resistant cold process built-up v roofingusin a solvent-thinned bituminous composition presents special prob-181118;

Accordingito this invention, a bituminous composition is provided whichis thinned with a volatile solvent for the bitumen in the composition sothat the composition can be applied cold, or, if desired in a slightlywarmed condition, to adhesively bond-the plies of a bituminous built-uproofing and which, in the finished roofing, not onl-yprovides a goodbond between the plies, but also possesses remarkably hish fireresistive propcitiesand imparts a'very high degree ot fire resistivenessto' the built-up roofing as a whole.

In our co-pendingtapplication Ser. No 497,805, filedAugust 7, 1943, forBuilt-up Roofing and CompositionsTherefor which has resulted in Patent-No.-2,424,234'for Compositions for Built-up Roofing, we have disclosedbituminous compositiens; and built-up i'oofing construction containing-'such'compositions, having.:high fire resistive The bituminouscompositions dis- 3 closed in our Patent No. 2,424,234 are of themopping-asphalt type, namely, adapted for spreading when heated on thejob, the bituminous composition being applied hot (usually at atemperature of the order of 350 F. to 425 F.) and the layers of feltbeing bonded thereto and together while the bituminous composition isstill in a heat plasticized condition. As distinguished from our PatentNo. 2,424,234, the invention of the present application is concernedwith a bi-.

tuminous composition which is suitablefor cold process application, thebitumen being reduced to a fiuid or semi-fluid consistency by thepresence of the volatile solvent and the tendency of some of thevolatile solvent to remain in the bituminous composition for longperiods of time presents special problems which have to be overcome ifthe composition as used in the built-up roofing is to have high fireresistance. These special problems are due primarily to the effect ofthe solvent in inducing the running and flowing of the bitumen so as tobe in a free burning condition regardless of the infiammabllity ornoninfiammability of the volatile solvent. We have found that for coldprocess application a different formulation of the non-volatileconstituents should be employed as compared with mopping asphaltcomposition disclosed in our Patent No. 2,424,234 as will be apparentfrom the disclosure of our present invention set forth hereinbelow.

ance with this invention within narrow and critical limits offormulation, and the chief features of our present invention are basedupon our discovering that by formulation within the defined limitationsof composition a solvent-thinned bituminous composition is providedwhich can be used in cold-process production of built-up roofings andwhich in the installed built-up roofing aiforols extraordinarily highresistance to fire.

, In order to facilitate an understanding of this inventiona typicalembodiment thereof will first be described for purposes ofexemplification. The composition of the example meets all of therequirements mentioned hereinabove, and after .the formulation of thetypical embodiment has been described, the critical factors essential tothis invention will be explained and defined in detail and applied tothe described typical em- The fire resistive bituminous composition;of

this invention results from a combination of a number of factors whichare explained and more fully defined hereinbelow. These factors includethe amount and softening point of the bitumen that is used, the amountsand kinds of different filler ingredients, the formulation of thecomposition as a whole, as well as the non-volatile base, within certainlimits of consistency. In general the bitumen has a softening point ofthe range 80 F. to 150 F. and constitutes about 30% to about 55% byweight of the non-volatile constituents, namely, the non-volatilebitumen and filler materials which are referred to hereinafter and inthe claims as the non-volatile baseiof. the compositions. The fillermaterial constitutes about to about 70% byweight of the nonvolatilebase. The filler comprises what is referred to herein and is definedmore in detail below as planar-extended filler. 'Such filler-has specialproperties which difier quite widely depending upon the particle size,and such properties are defined hereinbelow in terms of the gradingindex of the planar extended filler. The grading index of theplanar-extended filler must, be within certain limits in relation to theper cent. by Weight of the bitumen in the nonvolatile base. Finelyparticulate filler passing a 100 mesh testing sieve must also be presentwithin certain limits in relation to the per cent. by weight of bitumenin the non-volatile base. The non-volatile base must be within certainlimits of consistency as measured by the Wagner- Bowen plasticity valueat 400 F. which is defined hereinbelow and likewise the compositionbodiment.

In the following example, and elsewhere herein, the percentages givenare percentages by weight. One of the ingredients of the composition isasbestos dust. Asbestos dust which passes a 6 mesh standard testingsieve and is retained on an 8 mesh standard testing sieve is indicatedfor purposes'of brevity as (6+8). Other screen gradings are indicatedsimilarly. The non-volatile base of the composition of the typicalexample contains the following constituents:

Non-volatile base 1 Per cent Asphalt (130 F. softening point) 40Asbestos dust gradings Total asbestos dust"; 15 Kaolinitic clay (mostly-200) 45 The non-volatile base above stated is combined witha volatilesolvent, the proportions for the purpose of this specific example being15% by weight (on the composition as a whole) of solvent and 85% byweight of the non-volatile base so that the solvent thinned compositionhas the following formulation:

4 Per cent Asphalt (130 F. softening point) 34 Asbestos dust 13Kaolinitic clay 38 Solvent 15 as a whole, including the solvent, must bewithij.

in certain limits of Wagner-Bowen plasticity value at 77 F. which isdefined hereinbelow. For preferred embodiments, solvents which arecapable of affording low viscosity characteristics are employed andwhich, as a result,-have a speworkable at normal atmospherictemperatures cial effect in reducing fiame spread after the com positionis incorporated in a built-up roofing.

It is seen from the foregoing thatthe special fire resistive propertiesare obtained in accord- -The particular solvent employed in theforegoing example consists of petroleum naphtha having a boiling rangebetween 295 F. and 360 F.

The composition of the formulation above described may be prepared inany suitable way as by thinnin the asphalt with the solvent andincorporating the filler ingredients so that they become thoroughly anduniformly distributed.

The above described composition is easily and can be easily spread atsuch temperatures by use of a suitable implement so as to bond togetherthe plies of felt material of built-up roofing. In the installation ofbuilt-up roofing the i mposition zisisp eadt ou thickness; whereupon.the; wolatilez solvent begins to escape, making. 1,12hfi31s surfacetacky and stickyv Class C? ratingaare described briefirc. in 3.01113;

aforesaid Patents N os-.,:=,.2,326,-'Z23,wand: 2.326172%.v which testsare carried outiinrtstingbuilh-un roofings installed in; the .vmanner:aforesaid. Of these ratings gthev Class fCI! rating isgthe:lowestfire-retardant rating and ,servesmto :distinguish rooflngs having:appreciable"fire-retardant pron-1 erties from.roofingschavinglittleazorrno; fire re-; tardant properties suchtasuntreated .woodzshina gles; which, of course, are readilyrrignitedxandtend to'burn freely; The Class...A. .:rating is the. highestratingawarded by Underwriters? Laborae tories, Inc. anduis reserved:forsuchlhighlyfire azlayerrotzidesiredi,

retardant roofings asuasbestos-ycement shingles.

of the double coverage-type; ClassWB, is; an intermediate rating .and.is,. for,-example..;;. awardedto, single coverageasbestos-cementshingles.v So far as we are aware there isrno builteuproofing of the smooth surface, typepther-than that disclosed in ouraforesaid Patent-No. 2,424,234 that carries, or is entitled to eitherthe Class-A or Class B rating whether thewpliesot sheet material arecomposedof asbestos fiber and whether the bituminous waterproofing isapplied hot. with: out a volatile solvent or is .thinnedwithavolatilesolvent so as to be capable of. cold application. However, built-uproofings ofthe coldprocess type wherein the bitumen is thinnedwithavolatile solvent have been, prior'to. the. presentinvention,particularlydeficient in fire resistive properties. There are built-uproofingsmhich carry a higher fire retardant rating; whichlhigherratingisachieved by placing over the top ofthe built-up roofing, a very largeamount, such as 400 pounds or more per,l00. square feet, of somematerial such as crushed. rock; or. slag, that pro: tects. the roofings,from flame,-;but.use, ofrsuch large quantities of crushed,rock.or.slag.is;undesirable and, frequently as when' an inclined roofdeck is to be covered with built-rup roofingbcan not be used at all.

Built-up roofings or the general. construction shown in our aforesaidPatent 1 No. 2,42,234 which have been installed using the specialcoldprocess bituminous composition of this invention that have beendescribedabove by way. ofexample will successfullypass all of the, testsprescribed by Underwriters."Laboratories, Inc. for the Class A rating.Moreover, fordifiercnt numbers and arrangements of plies and usingpossible variations in the formulation ofthe special bituminouscomposition other built-uproofings within the scope of this inventionwillsuccessfully pass the Class A? and ClassafB.', fire retardant testsprescribed by Underwriters Laboratories,- Inc. In typicalconstructionof.a built-up roofing using the special bituminous. compositionvof thisinvention, the composition is applied .at normal temperature as to alayer of roofing ieltalreadyput in place, the volatile solvent ispermitted to partially evaporate therefrom causing; the bituminouscomposition tovbecome tacky and adher .sive, and, while the i bituminouscomposition.. is

in this: conditions-ano her never; otjt lt isimad adherent thereto,these operations being repeated have .very little effectincounteractingfioweven.

until the a desired. number. of plies haves been installed.

When ordinarily solvent thinned rbituminous compositions are used in theconstruction of built -up roofings, and. even when. ordinarygmoppingasphalt applied in wheat liquefied condition is. used in theconstruction'of built-up roofing,jthe bituminous material, when'thebuilt-up roofing is subjected: to theme retardant'tests prescribed byUnderwriters.Laboratories, Inc., tends to flow outfrom between the pliesof felt onto the surface exposed to the flame and burnswithconsiderablevigor. Moreover, the-.wind playing (over the test deck tendsto life uptheends-o-f the felt sheets so that the fire gets into the bodyof theroofing ;quite rapidly. Such roofings. are particularly vulnerable to,the fiame spread test. This is the caseeven though theupper surfaoeofthe:- built-up roofing does 'not carry, awate:rproofing layer of theasphalt.

By way of contrast, built-up roofin made with. the specialbituminouscomposition of this in-. ventionbehaves very diiferently whenexposed to fire. During exposure to the fiame the bitumen and filler inthe special bituminous composition remain in place due to the fact thatthe filler provides a stable skeletal mat in the bitumen, so that thebitumen instead of running out and burning carbonizes and forms withthe'filler a protecting mat-like layer that not only is highly resistantto combustion; but also has high'heat insulating effectiveness.Moreover, when amineral filler such as asbestos dust is present thatcontains: water of constitution liberatable at or adjacent fiametemperature small bubbles form in the residual mat-like massthatraugm'ent its heat insulating efiectiveness.

Hereinabove it has been pointed out thatthe special bituminouscomposition of this invention must be formulated within very closelimits which are critical to obtaining the desired high fire resistancewhen. the bituminous composition is incorporated in a built-up roofingand that the desired high fire resistance isdue to a combination offactors. One of these factors is the grading index of theplanar-extended fillercomponent of the bituminous composition. Theplanar-extended filler material is exemplified by fibrousfiller suchasasbestos fibers, cotton fibers, etc, and by plate like material suchasmica, the particles of which are thin relative to their lateralextent. Such fibrous fillers and platelike fillers are characterized bythe fact that at least onedimension is very small relative tolanothermore extended dimension, andsuch fibrous and plate-like fillers arereferred to generally herein as planar-extended? filler materialsthereby indicating that the particles are in the form of fibers or arein the form of plates having anextended dimension that isnconfinedessentially to only one ofthe three dimensionalplanes.

The grading index of a planar-extended filler is an index which isindicative of the effectiveness of a particular screen gradingor...mixture of screen gradings of planar-extended filler material inpromoting flow-resistance of a bituminous composition when. exposed toflame temperature. We have foundthat one of theia'ctors contributing tothefire resistanceof. a .bituminouslayer in. a roofing is that ofbeingresistant to flow when the roofing isexposedtofiame temperature. Fillareas a class have very little effect on such fiow when used in amountssuchas those used in conventional roofings and 'ordinary fillermaterials when used in relatively large amounts. We'

have found, however, that there is a point where'- at further additionsof filler material, even very small additions, result in a very greatincrease in flow resistance of the bituminous material and that there isa limited zone wherein the bituminous composition, when highly heated,will be stabilized against flowing, even though soft and highly plastic,due to the occurrence of a skeletal mat within the composition whichstabi- Iizes the composition and has the further effect of forming withthe bitumen a protective heat insulating mat-like mass that carbonizesin situ as a coherent, continuous protective layer that is highlyresistant to flame and transmission of heat.

The property of a filler material whereby a bitumen heated to adjacentflame temperature becomes stabilized and resistant to flow is a definitephysical property of the filler material that is similar to suchproperties as solubility, eifect of dissolved salts on boiling point,etc. Moreover, the property is capable of accurate measurement,according to a test procedure which we have devised in order toaccurately define the invention which is the result of our research anddiscoveries. This test procedure enables us to measure the flowresistance of 'a particular filler or filler mixture under conditions ofactual exposure to fire. For determining the flow resistance coefficientof a filler contained in the bituminous composition of this inventionthe bituminous composition is applied in a solvent thinned condition andthe solvent is permitted to evaporate until less than 1% by weight ofthe solvent remains, the test being made on the essentially non-volatilebase of the composition. The resulting bituminous layer, as disposed onan inclined test deck, is exposed directly to flame under preciselycontrolled conditions determined by the construction and operation ofthe testing apparatus. The test employed is the test for measuring theflow resistance coefficient of a filler which, as regards both apparatusand test procedure, is described in our aforesaid Patent No. 2,42%,234except that in the preparation of the sample to be tested thesolvent-thinned bituminous composition is placed between the piles ofthe sample by initially applying it in the solvent thinned condition toone or the other of the plies, permitting the solvent to evaporate untilthe bituminous composition becomes tacky and adhesive, applying theother ply to the tacky surface thereof, and placing the sample in adrying oven at about 170 F. until the solvent has been driven off andless than 1% by weight of the solvent remains. The thickness and weightof the resulting layer should be the same as that mentioned in ourPatent No. 2,424,234. as prescribed for the test.

The coefficient of flow resistance is computed according to thefollowing expression:

Weight of total collected bituminous composition X 100 Weight ofbituminous ico- composition in exposed area For example, if the weightof the bituminous If none of the coating of bituminous compositionflowsinto the pan or onto the exposed portion of ply 13a, then the flowresistance coeflicient is 100, which is the maximum attainable.

The non-volatile base of the bituminous composition of the inventionshould be such that the filler has a fiow resistance coefficient of orgreater, although in preferred embodiments of the present invention thefiller has a flow resistant coeiiicient between and 100. The filleremployed in the non-volatile base of the example of the presentinvention that has been described hereinabove, has a flow resistancecoefficient of substantially 95. 7

As stated above, We have found that it is essential that the bituminouscomposition of this invention contains a planar-extended fillermaterial. We have likewise found that the amount of planar-extendedfiller material that is required depends to a large extent upon thescreen analysis of the different screen fractions contained therein, forthe different screen fractions are widely different in theireffectiveness in imparting flow resistance. This can be illustrated inthe case of asbestos dust which is the planarextended filler materialthat is employed in the above-described typical embodiment of thisinvention. In the case of chrysotile asbestos dust, we have found thatwhen the screen grading (-28+35) is used and the non-volatile base ofthe composition contains 6.5% by weight of such specially graded fibers,53.5% by weight of kaolinitic clay (mostly -200), (total filler 60%) and40% by weight of asphalt having a softening point of about F., thenon-volatile base has a flow resistance coefiicient of about 75. Thescreen grading (8+10) is considerably more effective since a flowresistance coefiicient of 75 can be achieved when the non-volatile basecontains only about .66% by weight of such mineral fiber together with59.34% of the kaolinitic clay '(total filler 60%) and 40% of the sameasphalt.

In other words, using the same total amount of filler consisting ofasbestos fiber plus diluent filler that has little flow resistanceeffectiveness in amounts less than 60% by weight, the coarse fraction(8+10) is much more eifective than the fraction (-28-1-35) in affordinga given degree of flow resistance for the non-volatile base. On theother hand, if asbestos fiber (200) is used, it requires about 25% byweight of such fiber to achieve a flow resistance coefficient of about75'. The efiectiveness of the fibrous filler in the composition justmentioned, and the sur prising effect of only .66% of the (-8+10)fraction, is evidenced by the fact that a non-volatile base consistingof 60% by weight of the same kaolinitic clay and 40% by weight of thesame asphalt, has a flow resistance coefficient of only about 33.

In view of the differences in efiectiveness of the different screengradings of a planar-extended filler, such" as asbestos dust, we have,in order to accurately define the planar-extended filler component ofthe non-volatile base of the bituminous composition of this invention,assigned to the different screen gradings of planarextended fillers whatwe have called a screen factor for each of the different gradings. Thescreen grading of "(-28+35) of chrysotile asbestos fiber has been takenas having a value of unity. Therefore any screen grading that requiresonly half the amount to achieve the same flow resistance coefiicient ascompared with the amount of the grading :-(28j-35) will be twice asaqsinao effective and will have a screen factor of .2. On the otherhand, ascreen grading which requires twicethe amount ascompared'with'the amount "of the grading (-28+"35) will only have halfthe effectiveness and will have a screen factor of 0.5. In like mannerscreen factors can be assigned'to the other screen gradings.

The above-described test for determining the flow resistance coefiicientof a filler 'in the non volatile base of abituminous composition aiiordsa each screen "grading togethen'the grading index convenient basis forsetting up the screen factors of the screen gradings of theplanar-extended fillers on a definite scale, and when the screen "factorof a planar-extended'flller is referred to herein, the screen factor asdetermined in the following manner, is intended. The test fordetermining the flow resistance coeflicient is carried out using thetest apparatus and procedure abovedescribed. The total filler in allcases is 60% by weight of the non-volatile base and "the asphalt in allcases is an oxidized 'straiight'run asphalt having a softening point ofabout 135 F. Kao linitic clay, substantially all of which passes aZ'OO-me'sh testing sieve, is used "in all cases as the standard diluentfiller, and the amount by weight of a'particu'lar screen grading ofp'lanarextended filler to achieve a flow resistance coeflicient of '75,is determined. "Each -sample *is prepared using the materials andconstruction of the test sample as described hereinabove.

By way of concrete examplefit has been mentionedabovethat chrysotileasbestos *fiber of the screen grading "(-284-35) is taken :as having ascreen factor of unity. It being the case that 6.5% by *weight of thenon-volatile base of chrystolite asbestos dust of the screen grading(---28+35)the total filler being 60% asafore- -said--istrequired toafford a flow resistance coefiicient ref '75, Land it also being thecase that aboutz66-'% by weight of the non-volatilebaseof the screen:grading -(--8+ 1'0), (the total filler being 60%.), :also affords aflow resistance co eflicient of about75,.the screen factor of chrysotile asbestos dust of the'fscreen grading '(8+1!i) is 'seento be about.10. :By way of'further illustration, the fscreen :factors of thedifferent screen gradings of a typical chrysotileasbestos dust on thebases above-mentioned, are as follows:

It is to-be noted thatdnthercase of the .asbestos fiber of the screengrading -(200), .it. .required about .25 .of :the non-volatile baseto-achieve 1a flow resistance .coeflicient .of .75 and .that the screenfactor .25 .has been (assigned to this particular grading. Similarly,.any .grading of different type .of ..planar-extended filler whichrequiresmore than-% .by .weightof the monvolatile base .of.the..bituminous. composition to afford a flow resistance c'oe'flicientof about 7:5,.is to be considered as havingga screenfactor of .2.

'The foregoing. affords-"a convenient wayofas-.

of the total asbestos fiber is readily determined. By way ofillustration, the grading index of the mineral fibercomponent of thenon-volatile base of the above-mentioned typical embodiment of thebituminous-composition of this invention is as follows:

a 4 a y eig creen ra in 50mm Grad-mg of Compo- Factor Index ,sition .or30 .30 04 10 40 .1 4 -10 3 2. 5 1. 0 1. 5 1. 50 [2. 5 :1 2. 50 2. 0 8 1.50 1. 25 (ii 75 1. 0 .15 50 1. O '1 40 L3 35 .15 4. 5 i 25 1. 10

.fllotalgrading indexoi asbestos-fiber 10. 65

In determining the screen fractions or gradings of fibrous or othermineralfiller that are referred to herein, 8 inch diameter testingsieves of the W. S. Tyler Company Sieve Series, meeting A. S. T. M.Standard Ell-39 for Sieves for Testing'Purposeshav'e been used. Aquantity of filler to be screened ranging from 200 to 3.00 grams isplacedin the uppermost of a series of testing sieves and subjected tosuitable agitation as in azstandard "W; S.Tyler CompanyRo-Tap sievesh'akingmachine fora period offive minutes in order to "separatethe.origina1 filler roughly into fractions retained in the differenttesting sieves. "This operationisrepeated if necessary in order toobtain about to 200 grams of the desired screen fraction, which fractionis then individually :re-screenetl for "l5minutes using the Ro-Iap sieveshaking machine or its equivalent in order to remove "any' finescontained therein. The resultingscreenfraction is material that haspassed the "coarser. screen and is retained on the finer screen.

--When reference is .made herein to 'screen factor and -g-rading index;the reference is made to those values when determined under "thespecific conditions above-specified. -When, however, referenceiis made-to the flow resistance .coefiicient .of the .filler material in thenow-volatile base of a bituminous composition, the reference is to theflow resistance coeflicient of the entire filler .content of thecomposition whatever "the amountmay be and whatever the character of thebitumen, used in-the composition maybe, the non-.volatile base being:tested, :-however, on a sample that ;.is .of the construction andasphaltsaturated felt material, above specified.

The planar-extended. filler. that vispreferred in the .practice of .this,invention is asbestiform mineral .fiber, ,chrysotile asbestos dustbeing especially desirable. .O ther asbestiformlmineral fibersoftheparticlesize mentioned may likewise beemployefcl, such as Canadianpicrolite, .amosite,

, an ophy lit tremnlh and n Another suitable fibrous mineral is acomcertaining thefiow resistance effectiveness ."of a 7; minuted ,lnixill e vgof lhydrated Portland ecem ent and asbestos fiber, the hydratedPortland cement having become set with the asbestos fiber distributedtherethrough. A convenient source of such material is asbestos-cementroofing scrap which usually contains about to by weight of asbestosfiber and about 65% to 80% of hydrated Portland cement. Heretofore suchscrap has been regarded as an unavoidable waste of no commercial value.However, by subjecting the scrap to a disintegrator, such as a hammermill, the resulting mass contains a multiplicity of short asbestosfibers to which the hydrated Portland cement adheres as nodules and forthis reason this material is fibrous and is to be included in the termfibrous mineral.

Another material which is somewhat simi ar to asbestos-cement in thatthe material contains mineral fibers together with some non-fibrousmaterial, is disinte rated fiber-bearing serpentine rock. Since disintgrated fiber-bearing serpentine rock contains fibrous particles, suchdisintegrated serpentine rock is regarded as one form of fibrous mineralwhich is suitable for use in practicing this invention. Howe er,depending upon the physical structure and fibrous mineral content of theparticular serpentine rock that is used, the pro ortion of fibercontained therein is sub ect'to some variation. but, as pointed out beow, this merely has the effect of varying somewhat the screen factors ofthe various screen gradin s of the disinte rated serpentine rock as calculated to chrysot le asbestos dust of the scr en grading 28+35)whichhas a screen factor of unity. 'Moreover, disintegrated fib rbearinser entine rock is of such character that in order to liberate thefibrous material contained therein. it should pass a 20-mesh testinsieve, and. when reference is made herein to disintegrated fiber-bearingser entine rock. onlv that s r entine rock which has been disintegratedso that it asses a 20- mesh testing sieve is intended, since individualarticles of coarser radings are not fibrous in character but granu ar(are not fibrous mineral as this term is used herein) and since suchcoarser gradin s are ineffective in pro ucing highly fire-resistantroofings.

While fibrous mineral fillers selected from the group consistin ofasbestiform mineral fibers, disintegrated asbestos-cement and disintegraed fiber-bearin serpentine rock are preferred, other mineral fibers mavlikewise be em loyed, such as mineral wool and glass fibers. The'term"mineral wool inclu es various roducts obtained by attenuating intofibrous form suitable fused materials. such as rock or slag. In additionto fibrous minerals, other fibrous fil ers may be emplo ed as theplanar-e tend d filler component of the bituminous com osition of thisinvention although the mineral fibers are preferable for use in theractice'of this invention and it is desirable that a major proportion bywei ht of the planar-extended filler consist of asbestiform mineralfibers. Thus, any of a wide selection of animal, vegetable and syntheticfibers may be used. Cotton is suitable and, in the very shortgrades isinexpensive and, in fact, has little commercial value.

In addition to cotton, one may employ wood fibers. such as fine sawdust,or defibrated wood and aper and paner fibers, such as round wood.sulphite, and kraft paper pulps. Finely divided wool fiber is alsosuitable but is much more costly. Synthetic fibers. such as regeneratedce lulose (rayon) and cellulose acetate also may be used.

In addition to fibrous fillers, another filler that is similar tofibrous fillers in that it is effective in varying degrees dependingupon the screen grading ormixture of screen gradings that is employed,is mica. Mica is characterized by its occurrence in the form of smallplates which are thin relative to their lateral extent. Mica and fibrousmaterials are characterized by the fact that at least one dimension isvery small relative to another more extended dimension, and, as statedabove, are referred to herein under the generic term planar-extendedfiller material. In the case of the filler, such as mica that exists inthe form of thin plates, particles which are retained on a l l-meshtesting sieve are undesirable in the composition. With regard to fibrousfillers other than asbestiform mineral fibers, it is not usually thecase that a particular screen grading of, for example, asbestos-cement,cotton, wood fiber, etc, will have the same screen factor as that ofchrysotile asbestos fiber.- In fact, even as many different types ofasbestiform mineral fiber there are some variations in this regard.However, utilizing chrysotile asbestos dust as the standard, chrysotileasbestos dust of the screen grading (-28+35)' having a value of unity,the screen factor of the screen grading of other fibrous fillers isdeterminable in the same way that the screen factor of the differentscreen gradings of chrysotile asbestos fiber is determinable as has beendescribed hereinabove. However, fibrous fillers, particularly in thecase of wood fibers, cotton and the like, are subject to considerablevariation, and for this reason the screen factor and grading index hasbeen calculated to chrysotile asbestos fiber, which is more uniform inits physical characteristics, as the standard; The foregoing, withrespect to the screen factors of other fibrous fillers, also applies toplanar-extended fillers of the plate type. For example, the screenfactor of mica of the screen grading (-28+35) is about 0.9; 'Theforegoing also applies to the screen factors of mixtures ofplanarextended fillers, calculated to chrysotile asbestos dust of thescreen grading (-28+35) as the standard.

In ascertaining the grading index of a filler of the planar-extended.type for use in a bituminous composition for cold process application inthe construction of built-up roofing, the grading index required willvary with the amount of bitumen in the bituminous composition, theamount of bitumen being, of course, an inverse function ofthe totalfiller. When the amount of waterproofing bitumen in the non-volatilebase of the composition is about 30% by weight, the grading in-. dex ofthe planar extended filler is desirably at least about 4, while for atotal bitumen content of the non-volatile base of about 55% by weight,

the grading index for obtaining similar stabilization of the bitumenwill be at least about 8. For bitumen contents of the non-volatile baseranging from 30% by weight to 55% by weight, the minimum requiredgrading index: varies proportionally from about 4 to about 8respectively, More generally, in the practice of this invention,

it is desirable to employ filler of the planar-ex tended particle typehaving a grading index the ratio of which to the percent by weight ofwaterproofing bitumen in the non-volatile base is at leastabout 1 to 8,and preferably is at least about When a filler of thefplanar-extendedtype is used, such filler should'be used in the finely-diyideddust-lilge formas distinguished from long 13 cotton, wood, orasbestos fibers. Fibrous fillers that are retained one 6 meshtestingsieveareundesirable in the coating composition. It has beenmentioned above that mica retained on a 14 mesh testing sieve isundesirable. Accordingly, and somewhat more generally, it is desirablethat the filler materialof the planar-extended typ be confined to thatwhich passes a 6 mesh testing sieve and which does not have more thanone di mension greater than about .046 inch, which is the width of theopening in a 1ft mesh testing sieve. When-a filler of theplanar-extended type is used that is coarser than has been mentionedabove, such filler material tends to form into clumps or clots whichrender the solvent-thinned bituminous composition unspreadablewithdesired uniformity and also impairs the fire resistance of the appliedcoating dueto occurrence of zones of insufficient protection and due touneven andpoor adhesion to the plies of felt or the like contained inthe built-up roofing. For this reason, it is highly desirable to limitthe quantity of coarser planar-extended filler to that which can beincorporated in a bituminous composition that, when thinned withavolatile solvent to the usually desirable that'less than 10% by weightof the total non-volatile base of the bituminous composition consist ofa filler of the planar=extended type which isretained on a 14 meshtesting sieve, although in-the case of mineral wool a sub- *stantially"greater proportion'of such coarse material can be incorporated in aspreadable composition. While the presence of any fiber retained on a 6mesh testing sieve isregarded asundesir- "able and while thepresence-ofany mica retained on a l l mesh testing sieve is regardedas undesirable,any small quantity of such excessively coarse planar-extended fillerthatmay be present while still retaining spreadability is to be regarded ashavingascreen factor of 40. Usually it is desirable that the ratio ofgrading index of the filler of the planar extended type to the per cent.by weight of the bitumen in the composition to be less than about 1to1.7, and preferably'less than about i to 2.5; so as to avoid theinclusion of'an excessive quantity of the 'coarser screen fractions.

As stated hereinabove, the total filler contained in the non-volatilebase of bituminous composi "tion of thisinvention is of the order of to70% by weight of the non-volatile base. Preferabl'y, the fillerconstitutes from to 65 by weight of the non-volatile base. While thefiller may consist entirely of filler particles of the planar-extendedtype, provided such filler is used within the aforesaid limits ofgrading index in relation to the bitumen content of the non-volatilebase, it is preferable, and constitutes normal practice of thisinvention, to include a diluent filler that is not of theplanar-extended type. In addition to kaolinitic clay, there are a numberof other heat-resistant mineral fillers which may be employed, e. -gslate 'fiour, limestone dusnjsilica flour, other clays, talc, fly ash,hydrate'd'Portland "cement, dead burned calciumsulphate, andprecipitated calcium silicate hydrate. Most fillers of 14 this characterare of such state of subdivision that about% by-weight thereof will passa .100 mesh testing sieve.

In addition tomineral fillers, organic lillermateri'als may be employed,although it is usually advantageous to employ a heat-resistant mineralin an amount such that the ratio of the per cent. by weight ofheat-resistant mineral filler in the non-volatile base of the bituminouscomposition to the per cent. by weight of waterproofing bitumen in thebituminous composition is at least 1 to 3 and even more desirably atleast 1 to 2. By heat-resistant, any material that retains. structuralintegrity when a bituminous composition containing it is exposed toflame temperatures is intended and any material such as chrysotileasbestos, kaolin clay, hydrated Portland cement or the like thatcontains water of constitution liberatable at or below flame temperatureis regarded as heat-resistant. The foregoing respecting the proportionof heat-resistant mineral filler in the non-volatile base applies to thetotal filler including the planar-extended type filler and any di1uentfiller used in conjunction therewith.

.Among the organic fillers, examples of "such fillers of theplanar-extended type have been given hereinabove. Examples ofnon-planarextended organic filler materials which may be employed arefinely-divided cork, coal, coke, ground hard rubber, ground syntheticresins such as phenol-aldehyde resins) pyrobitumens, and the like. 1

li'li'ore generally, any'linely-divided solid waterinsoluble filler orfiller mixture may be employed provided'the filler material has asoftening point "above about 500 F. and preferably above about Til indetermining the'softeninlg point of the filler 'material, the standardcube-in-air softening point test isreferred to.

In formulating the bituminous composition of this invention, we havefound it essential that the filler include particles which are.suiilciently finely-divided to pass a mesh testing sieve. The particlespassing a 100 mesh testing sieve may be any of the constituent particlespassing a 100 mesh testing" sieve that are contained in the bituminouscomposition, namely, may be either of the planar-extended type, ordiluent filler not of the planar-extended type, or a mixture of both. Wehave found that for total filler contents of the non-volatile baseranging from 45 to 70 by weight, the filler particles passing a 100 meshtesting sieve should vary from at least'about'20 to at" least about-40%by weight, and preferably from at'least-about 30'%--'to at leastabout-50% by weight, proportionally. "The presence of suchfinely-divided filler assists in preventing migration of the bitumenupon 'exposure of the bituminous composition to flame temperature andreduces combustibility and flame spread. Such finely-divided filler alsoimproves the application consistency of the bituminous composition whenin solvent-thinned condition suitable for cold process application.

For the preferredrange of total filler content,

namely, 55% to 65% by weight of the nonvolatile base, the fillerparticles passing a 100 mesh testing sieve should vary from at leastabout 28% to at least about 35%, and preferably from at leastv about 35%to at leastabout 45% by weight, proportionally.

The presence. of. excessively coarse planarnon-planareextended filler isalso undesirable.

. 15 For this reason, it is desirable that the amount ofnon-planar-extended filler retained on a 14 mesh testing sieveconstitute less than by weight of the non-volatile baseof the bituminouscomposition.

Of the fillers other than planar-extendedtype filler, we prefer toemploy kaolinitic type clay, since we have found that the specialbituminous compositions of this invention that contain kaolinitic typeclay are particularly effective in preventing the separation of theplies of built-up roofing when the roofing is exposed to flametemperature. It is desirable, therefore, that the non-volatile base ofthe special bituminous composition of this invention contain at least15% and preferably at least 25% by weight of kaolinitic clay.

Of the filler materials above-mentioned, chrysotile asbestos fiber andCanadian picrolite usually contain about 12% to 15% of water ofconstitution liberatable at temperatures ap proaching flame temperature.Other asbestiform mineral fibers are low in water of constitution. Someof the non-fibrous'flller materials contain Water of constitution thatis liberatable at or adjacent flame temperature. Thus kaolinitic typeclays, powdered serpentine rock, calcium silicate hydrate and hydratedPortland cement contain or more of water of constitution that isliberatable at or below flame temperatures. When the filler materialcontains water of constitution liberatable at or below flametemperature, the liberation of moisture causes the bituminouscomposition as disposed in a built-up roofing to develop pores to agreater extent than otherwise when the bituminous composition is exposedto flame temperature and this is desirable since the pores tend toaugment the heat insulating efiiciency of the matlike residue that isformed upon exposure of the bituminous composition to flame temperature.It is desirable that the bituminous composition of this inventionhave'incorporated therein a filler material containing water ofconstitution, which water of constitution is liberatable at or belowflame temperature, that amounts to at leas about 5% by weigh of thenon-volatile base of the bituminous composition.

In order that there may be a proper overall proportioning of anyparticular filler or filler mixture to the bitumen, we have found thatit is also essential that the non-volatile base of the bituminouscomposition be formulated within certain limits of plasticity valuewhich has been determined by us, using a Wagner-Bowen mixing bowlplasticimeter, manufactured by E. E. W. Bowen, Bethesda, Maryland, inthe modified form illustrated and described in our aforesaid Patent Inthe formulation of the bituminous composition of this inventionthe'Wagner-Bowen plasticity value at 400 F. of the non-volatile base of thebituminous composition should be greater than 250 grams but should beless than 1000 grams.

the above described specific examplepf the invention is about 315 grams.The foregoing Wagner-Bowen plasticityvalues are determined using theWagner-Bowen plasticimeter and the test procedure with reference theretothat are fully disclosed in our aforesaid Patent No. 2,424;-

234 and reference herein or in'the claims to the 16 Wagner-Bowenplasticity value at 400 F. of the non-volatile base of the bituminouscomposition of this invention is to such pasticity value as .sodetermined.

It is also important that the bituminous composition as formulated insolvent-thinned condition for cold process application in theconstruction of built-up roofings be formulated within predeterminedlimits of Wagner-Bowen plasticity value at 77 F. The Wagner-Bowenplasticimeter that is used for making this determination is identicalwith that referred to hereinabove and described and illustrated in ouraforesaid Patent No. 2,424,234 except that a diiferent type of drag toolis employed. Thus instead of using the drag tool shown in Figs. 19 and20 and in detail in Figs. 21A and 21B of the drawing of our said patent,the drag tool used is in the form of a simple 'rod inch in diameterwhich extends horizontally from the collar I28 fixed to the verticalshaft I21 and which has a shorter end portion bent downwardly so as tobe to the horizontal portion for penetratin below the surface of thebituminous material in the mixing bowl of the plasticimeter. Theforegoing reference characters are those appearing in the drawing of ourPatent No. 2,424,234 and the direction of the emanation of thehorizontal portion of the rod from the shaft 121 is the same as that ofthe rod I46 comprised in the drag tool shown in Patent No. 2,424,234.The length of the horizontal portion of the rod measured from the axisof the shaft I21 to the axis of the turned down end portion of the rodis 4 /8 inches. The distance from the axis of the horizontal portion ofthe rod to the tip of the turned down end portion is 13% inches. Thedistance between the tip of the turned down end portion of the rod andthe upper surface of the bottom of the bowl of the plasticimeter isinch. The turned down end portion of the rod is directed downwardly atan angle of 33 to the vertical in the clockwise direction as regardsrotation of the bowl of the plasticimeter about its axis. In carrying'out the test for determining the Wagner- Bowen plasticity value at 77the depth of the composition in the mixing bowl as it passes the dragtool is one inch, and the lower end of the measuring rod which acts asan indicator respectin the proper depth of the composition in the bowlas shown in our Patent No. 2,424,234 is ad- J'usted so as to be one inchfrom the bottom of the bowl; Except for the difference in the natureofthe drag tool and for the difference in the depth of the composition inthe plasticimeter bowl as it passes the drag tool and for the differencein the temperature maintained in the test, the measurement of theWagner-Bowen plasticity value at 77 F. of a solvent-thinned compositionis as described and illustrated in our Patent No. 2,424,234 andreference herein or in the claims to such value is to such value as sodetermined with the changes described. In formulating the bituminouscomposition in solvent-thinned condition we have found that theWagner-Bowen plasticity value at 77 F. should be between 15 and gramsand preferably is between 25 and 75 grams. The Wagner-Bowen plasticityvalue at 77 F. of the solvent-thinned composition of the above describedexample of this invention is about 52 grams.

With regard to the bitumen that is employed, it has been pointed outabove that the softening point of the bitumen may be between 80 F. andF. and that the per cent. by weight thereof on the non-volatile base maybe between 30% 17 and 55%. However, in

bitumen used'has a r e re a t et e softening point between 115 F. and135 F. and constitutes from about 35% to about 45% by weight ofthe nonvolatile base of the bituminous composition. The softening pointsreferred to are determinedby-the standard ring and ball softening pointtest. Asphalts from Mid-Continent crudes are desirable although otherasphalts are suitable, such as those'obtained from Mexican, Venezuelan,andColom-bian crudes. Moreover, other bitumens, such as pitches, coaltar and the like may also beused in the practice of this invention.We-have found that the now resistance coefficient of a "given amount offiller is usually somewhat higher inthe case of a cracked asphaltascompared with other types of asphalt, andfor'thisreason may be'advantageously employed especially ln's'ubs'tra e! a built-up roofingwhere there is-to "belittle-direct When, however, the

exposure to the weather. special bituminous composition of thisinvention is to be used for direct exposure to the weather, it isusually preferably to employ some bituminous or asphaltic material otherthan cracked asphalt as all, or as the major proportion of, the bitumencontent of the non-volatile base of the special bituminous composition.

When reference is made herein to "bitumen," this term is used inreference to asphalt, pitch, tar or the like by itselfand unmixedwith'filler; When, on the other hand, referenceis madeherein tobituminous composition or a bituminous ma.- terial Or a bituminouslayer, reference "is made to a composition, material or layer comprisingbitumen either with or without filler. Any modifier, e. g., of aresinous or oily character that may be mixed with the bitumen'is to beregarded as part of the bitumen content of the compositionl Thebituminous composition as made up for cold process built-up roofing has,of course, a solvent for the bitumen in the composition so that thesolvent that is present, by dissolving the bitumen, will reduce thebituminous composition to the desired condition of workability andspreada bility. The solvent that is employed shouldlikewise be of suchvolatility that after the solventthinned composition of this inventionhasbeen applied as a layer, the solvent will evaporate therefrom withina reasonable time and cause the layer of bituminous composition to setup because of loss of solvent therefrom. By volatile solvent, as thisterm is used herein and in the claims, the referenceis to a solventwhich is adapted to dissolve the bitumen in the bituminous compositionand which, m a bituminous composition such as that hereinabove describedas a typical example of the practice of this invention, exhibitsfugacity of the order of, or greater than, carbon tetrachloride. In thecase of inflammable solvents, it is ordinarily desirable that thesolvent not have a flash point below about 80 F.

Any of the solvents for bitumen may be employed, examples bein petroleumfractions of suitable volatility and flash point, those supplied in thenaphtha class being preferable.

Turpentine is also suitable.

In addition to the foregoing non-inflammable solvents, solvents such ascarbon tetrachloride and tetrachlorethylene may be used. With regard tothe employment of non-inflammableisolvents, we have found as a result ofourfresearch that use of non-inflammable solvents contributes onlyslightly to the fire resistive properties applicationin the constructionof 18 of the s pecial'bltuminous composition of this invention'.

While any volatile solvent for the bitumen in the bituminous compositionmay be employed in the practice of this invention, we have found thatthe fire resistive properties of the composition are very markedlyimproved by employment of a solvent having a high solvent power for thebitumen in the bituminous composition, namely, one which reduces thesolvent-thinned composition to within the limits of Wagner-Bowenplasticityvalue at 77 F. that have been set forth above (15 to 125grams) when employed in rela tively small proportion in the bituminouscompcsition. 'Qrdinarily it preferable to employ a solvent which reducesthe bituminous composition to within theaforesaid limits of Wagnerwenplasticity value at 77 F, when the solvent constitutes 35% or lesser thebituminous composition, and for obtaiiung optimum results the solventconstitutes not morethan 20% by weight of the bituminous composition. Inordinary practice we have found that the best results from the point ofview of fire resistance are obtained when the solvent is present withinthe aforesaid limits while maintaining the Wagner-Bowen plasticity valueat 77 F. within the preferred limits above stated for the'value, namely,25 to grams. 'It is also desirable to employ in preferred embodiments asolventof high fugacity, namely. a solvent which, in a bituminouscomposition suoh as that of the above described typical example of thepractice of this invention, exhibits a fugaoity of the order of, orgreater than, petroleum naphtha of the boiling range 300 F. to 400 F.,and any such solventis referred to herein and in the claims as a highlyfugitive solvent for the bitumen.

The foregoing regarding the f-ugacity and solvent power ofthe solvent isof importance in attaining high fire resistive properties when thebituminous composition is employed as a substratum' in the body of abuilt-up roofing (namely, under an overlying layer of felt or the like),since we have found that the fire resistive n ss r the roofing isadversely aifected by the retention of volatile solvent, whether thesolvent is inflammable or non-inflammable, due to the'tendency ofretained solvent to induce flow of bitumen which in turn inducesflammability and c'ombustibility' In the construction of builtup roofingby cold process application of bituminous composition, sheet materialthat overlies a layer of the special bituminous composition isnecessarily put in place while the layer of bituminous composition isstill somewhat tacky and adhesive due to presence of some retainedsolvent. This retained solvent thereafter becomes entrapped and manymonths may elapse before the amount of retained solvent becomesmaterially reduced as a result of gradual per meation to and escape froman outer surface of the roofing. We have found that the retention ofsolvent in built-up roofing made from solvent-thinned bituminouscomposition constitutes the chief reason why this type of built-uproofing has presented a particularly great fire hazzard and why theproblem of affording high fire resistance in the case of this type ofbuilt-up roofing is especially difiicult. The problem of attainingpighfire resistance in connection with this type of built-up IOOfillg hasbeen largely attained by'the special formulation of the nonvolatile baseof the bituminous composition. However, it is important in attainingvery high 193isi640 fire resistance according to this invention that thesolvent used be of the type and amount hereinabove defined.

While the composition of this invention is ordinarily made up so as tobe suitable for application at ordinary atmospheric temperatures, it isnot without the scope of this invention to subject the composition tomild heating, e. g., in cold weather, to increase the fluidity of thecomposition for application and such mild heating is not inconsistentwith cold-process application as distinguished fromthe hot applicationof ordinary mopping asphalt at temperatures of the order of 300 F.t 350F. It is apparent that compositions other than the specificexamplehereinabove given of a typical embodiment of this invention will meetthe. requirements of the definition hereinabove stated for thosebituminous compositions which are adapted for cold process production ofbuilt-up roofings having high fire resistance although the narrownessand criticality of the limitations imposed by the definition of thisinvention confine the possible variations within close limits offormulation.

While reference has been made hereinabove to the employment of feltconsisting of organic fibers or asbestos fibers, and to the impregnationof felt with a bituminous waterproofing material, it is apparent thatany other sheet-like strainresisting material can be employed in thefabrication of built-up roofings employing the special fire resistantbituminous composition of this invention. Thus sheets of woven fabricsuch as canvas or duck may be employed, or sheets of unspun fibrousmaterial and generally any type of fibrous sheet-like base material,either foraminous or non-foraminous, and impregnated or unimpregnated,may be employed. Moreover,

the impregnating material for the fibrous sheet may be bituminous orsome other type of hinder .or waterproofing material.

The bituminous composition of this invention may be used for otherpurposes than the construction of built-up roofing and is suitablegenerally as a cementing composition for applica' tion to surfaces andfor binding plies of sheet material together with a waterproofingbituminous layer. While the composition as applied contains the volatilesolvent, the volatile solvent gradually evaporates during and afterapplication. The non-volatile constituents of the composition of thisinvention afford the high fire resistive properties that have beenreferred to hereinabove after the volatile solvent has been evaporatedand this invention relates both to the cementing composition in itssolvent thinned condition and to the cementing composition in" itswholly or partially dried condition as characterized by the formulatonof the non-volatile constituents.

While this invention has been described in conbase ofthe bituminouscomposition, and a volatile solvent. for the bitumen in saidnon-volatile base, said non-volatile base comprising about 35% to aboutby weight of bitumen having a softening point of the range 115 F. to 135F. and about to about by weight of finelydivided solid water-insolublefiller having a melting point above 500 F., said filler comprisingplanar-extended filler consisting of particles which pass a 6 meshtesting sieve and which do not have more than one dimension greater than.046 inch and the grading index of which has a ratio to the. percent; byweight of the bitumen in said non-volatile base of at least 1 to 5, theratio of the grading index of said planarextended filler to thepercentby weight of the bitumen in said non-volatile base being notgreater th'an about 1 to 2.5, said finely-divided solid water-insolublefiller comprising material passing a 100 mesh testing sieve'which is anyconstituent particles passing a 100 mesh testing sieve comprised in thetotal filler and which constitutes in said non-volatile base'at leastabout 35% to at least about 45% by weight of said non-volatile baseproportionally for total filler contents ranging from 55% to 65% byweight of said non-volatile base, said filler comprising heat-resistantmineral filler the ratio of the percent by weight of which in saidnonvolatile base to the percent by weight of bitumen in saidnon-volatile base is at least 1 to 2, said non-volatile base having aWagner-Bowen plasticity value at 400 F. greater than 275 grams and lessthan'700 grams, said volatile solvent constituting notgreater than 20%by weight of said bituminous composition and having iungacity insaid'composition at least as great as carbon tetrachloride, and saidbituminous composition as thinned by said solvent having a Wagner-Bowenplasticity value at 77 F. between 25 and grams.

2. A solvent-thinned bituminous cementing composition according to claim1 wherein said volatile solvent is a highly fugitive solvent.

3. A solvent-thinned bituminous cementing composition according to claim1 wherein said planar-extended mineral filler consists in majorproportion by weight of asbestiform mineral fibers.

GEORGE ARTHUR FASOLD. HAROLD W. GREIDER.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number OTHER REFERENCES v Petroleum Zeitschrift,1933, vol. 29, No. 45, pp. 1-12; Rosenberg: Micro-asbestos in theAsphalt Industry andRoad Construction.

1. A SOLVENT-THINNED BITUMINOUS CEMENTING COMPOSITION ADAPTED FORAPPLICATION TO PROVIDE A WATERPROOFING LAYER IN THE CONSTRUCTION OFBUILTUP ROOFING WHICH CONSISTS ESSENTIALLY OF NON-VOLATILE CONSTITUENTSCONSTITUTING THE NON-VOLATILE BASE OF THE BITUMINOUS COMPOSITION, AND AVOLATILE SOLVENT FOR THE BITUMEN IN SAID NON-VOLATILE BASE, SAIDNON-VOLATILE BASE COMPRISING ABOUT 35% TO ABOUT 45% BY WEIGHT OF BITUMENHAVING A SOFTENING POINT OF THE RANGE 115* F. TO 135* F. AND ABOUT 55%TO ABOUT 65% BY WEIGHT OF FINELYDIVIDED SOLID WATER-INSOLUBLE FILLERHAVING A MELTING POINT ABOVE 500* F., SAID FILLER COMPRISINGPLANAR-EXTENDED FILLER CONSISTING OF PARTICLES WHICH PASS A 6 MESHTESTING SIEVE AND WHICH DO NOT HAVE MORE THAN ONE DIMENSION GREATER THAN.046 INCH AND THE GRADING INDEX OF WHICH HAS A RATIO TO THE PERCENT BYWEIGHT OF THE BITUMEN IN SAID NON-VOLATILE BASE OF AT LEAST 1 TO 5, THERATIO OF THE GRADING INDEX OF SAID PLANAREXTENDED FILLER TO THE PERCENTBY WEIGHT OF THE BITUMEN IN SAID NON-VOLATILE BASE BEING NOT GREATERTHAN ABOUT 1 TO 2.5, SAID FINELY-DIVIDED SOLID WATER-INSOLUBLE FILLERCOMPRISING MATERIAL PASSING A 100-MESH TESTING SIEVE WHICH IS ANYCONSTITUENT PARTICLES PASSING A 100-MESH TESTING SIEVE COMPRISED IN THETOTAL FILLER AND WHICH CONSTITUTES IN SAID NON-VOLATILE BASE AT LEASTABOUT 35% TO AT LEAST ABOUT 45% BY WEIGHT OF SAID NON-VOLATILE BASEPROPORTIONALLY FOR TOTAL FILLER CONTENTS RANGING FROM 55% TO 65% BYWEIGHT OF SAID NON-VOLATILE BASE, SAID FILLER COMPRISING HEAT-RESISTANTMINERAL FILLER THE RATIO OF THE PERCENT BY WEIGHT OF WHICH IN SAIDNONVOLATILE BASE TO THE PERCENT BY WEIGHT OF BITUMEN IN SAIDNON-VOLATILE BASE IS AT LEAST 1 TO 2, SAID NON-VOLATILE BASE HAVING AWAGNER-BOWEN PLASTICITY VALUE AT 400* F. GREATER THAN 275 GRAMS AND LESSTHAN 700 GRAMS, SAID VOLATILE SOLVENT CONSTITUTING NOT GREATER THAN 20%BY WEIGHT OF SAID BITUMINOUS COMPOSITION AND HAVING FUNGACITY IN SAIDCOMPOSITION AT LEAST AS GREAT AS CARBON TETRACHLORIDE, AND SAIDBITUMINOUS COUMPOSITION AS THINNED BY SAID SOLVENT HAVING A WAGNER-BOWENPLASTICITY VALUE AT 77* F. BETWEEN 25 AND 75 GRAMS.